Nd isotope mapping of a Pinwarian-age composite arc belt in the Quebecia terrane of the central Grenville Province, Canada

2019 ◽  
Vol 332 ◽  
pp. 105409 ◽  
Author(s):  
Shannon Vautour ◽  
Alan Dickin
Keyword(s):  
Grenville Province ◽  
Nd Isotope

An application of Nd isotope mapping in structural geology: delineating an allochthonous Grenvillian terrane at North Bay, Ontario

2003 ◽  
Vol 140 (5) ◽  
pp. 539-548 ◽  
Author(s):  
A. P. DICKIN ◽  
R. H. MCNUTT
Keyword(s):  
Structural Geology ◽  
Amphibolite Facies ◽  
High Grade ◽  
Grenville Province ◽  
Nd Isotope ◽  
Bay Area ◽  
The North ◽  
Depleted Mantle ◽  
Different Types ◽  
Isotope Analyses

Fifty new Nd isotope analyses are presented from the North Bay area of the Grenville Province in Ontario. These data are used to map the extent of an allochthonous Grenvillian terrane which is an outlier of the Allochthonous Polycyclic Belt of the Grenville Province. Amphibolite facies orthogneisses from the allochthonous terrane have depleted mantle Nd model ages (TDM) below 1.8 Ga, whereas the gneisses of the structurally underlying parautochthon almost invariably have model ages above 1.8 Ga. The distribution of model ages is consistent with the distribution of distinct types of metabasic rock, used by other researchers as the criterion for recognizing rocks of the allochthonous and parautochthonous belts of the Grenville Province. The agreement between these different types of evidence demonstrates that Nd isotope mapping is a reliable and powerful tool for mapping terrane boundaries in high-grade metamorphic belts.

Nd isotope mapping of the Lac Dumoine thrust sheet: implications for large-scale crustal structure in the SW Grenville Province

Terra Nova ◽  
2012 ◽  
Vol 24 (5) ◽  
pp. 363-372 ◽  
Author(s):  
Alan P. Dickin ◽  
David Cooper ◽  
Anlin Guo ◽  
Cara Hutton ◽  
Chris Martin ◽  
...  
Keyword(s):  
Crustal Structure ◽  
Large Scale ◽  
Thrust Sheet ◽  
Grenville Province ◽  
Nd Isotope

Nd isotope mapping of the Allochthon Boundary Thrust on the shores of Georgian Bay, Ontario: significance for Grenvillian crustal structure and evolution

2015 ◽  
Vol 152 (6) ◽  
pp. 993-1008 ◽  
Author(s):  
ALAN DICKIN ◽  
ROBERT NORTH
Keyword(s):  
Crustal Structure ◽  
Large Scale ◽  
Geological Mapping ◽  
Grenville Province ◽  
Nd Isotope ◽  
Georgian Bay ◽  
Lithological Mapping ◽  
Depleted Mantle ◽  
Central Gneiss Belt ◽  
Tectonic Boundary

AbstractNearly 50 new Nd isotope analyses are presented for the Shawanaga region of Georgian Bay, Ontario, to study crustal evolution in the Grenvillian Central Gneiss Belt. Depleted mantle (TDM) Nd model ages are used to map a major Grenvillian tectonic boundary, the Allochthon Boundary Thrust (ABT), which in the Shawanaga area separates gneisses with TDM ages above and below 1.65 Ga. This is lower than the 1.8 Ga age cut-off observed further north, and is attributed to a southward increase in Mesoproterozoic magmatic reworking of an original Palaeoproterozoic continental margin, causing a progressive southward decrease in Nd model ages. Between Shawanaga Island and Franklin Island, Nd isotope mapping yields an ABT trajectory that closely matches published geological mapping, and passes within 100 m of four retrogressed eclogite bodies typically associated with the thrust boundary. This validation of the method gives confidence in the mapped trajectory south of Snake Island, where sparse outcrop inhibits lithological mapping. The new results suggest that published 1.7–1.9 Ga TDM ages in the Lower Go Home domain of the Central Gneiss Belt further south are also indicative of parautochthonous crust. Hence, we propose that the main ramp of the ABT is located in the immediate hangingwall of the Go Home domain, much further south than generally recognized. This has important implications for the large-scale crustal structure of the SW Grenville Province, suggesting that the ABT ramp has a similar curved trajectory to the Grenville Front and the Central Metasedimentary Belt boundary thrust.

A test of detailed Nd isotope mapping in the Grenville Province: delineating a duplex thrust sheet in the Kipawa–Mattawa region

2006 ◽  
Vol 43 (4) ◽  
pp. 421-432 ◽  
Author(s):  
M K Herrell ◽  
A P Dickin ◽  
W A Morris
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Data Sets ◽  
Aeromagnetic Data ◽  
Thrust Sheet ◽  
Grenville Province ◽  
Nd Isotope ◽  
Tectonic Model ◽  
Thrust Sheets ◽  
Archean Crust

Over sixty new neodymium model ages were determined on orthogneisses from the Kipawa–Mattawa region of the Grenville Province to refine previous Nd isotope mapping work in this area. The combined Nd data sets support a tectonic model involving three major thrust sheets in the Kipawa area, separated by major shear zones. The uppermost sheet is correlated with the Allochthonous Polycyclic Belt, represented in the study area by the Lac Watson nappe, along with two allochthonous klippen. These have Nd model ages < 1.8 Ga, consistent with previous work. Within the underlying Parautochthonous Belt, previous workers identified a second major shear zone, separating rocks with Archean and Proterozoic crystallization ages, respectively. These two thrust sheets also have distinct Nd isotope signatures. The lowermost sheet consists of metamorphosed but otherwise relatively pristine Archean crust with Nd model ages > 2.6 Ga, whereas the overlying sheet consists of magmatically reworked Archean parautochthon with model ages from 1.8–2.6 Ga. A residual magnetic-field map developed from aeromagnetic data was compared with the terrane boundaries determined from isotopic data. The aeromagnetic data accurately reflect the margin of relatively pristine Archean crust in the study area, but this boundary does not correspond to the Allochthon Boundary Thrust. Instead, this boundary resulted from downcutting of the basal shear zone of the allochthon. This caused décollement of the strongly reworked Archean parautochthon to generate a duplex thrust sheet that was transported northwestwards over pristine Archean crust.

The extent of juvenile crust in the Grenville Province: Nd isotope evidence

2009 ◽  
Vol 122 (5-6) ◽  
pp. 870-883 ◽  
Author(s):  
A. P. Dickin ◽  
R. H. McNutt ◽  
C. Martin ◽  
A. Guo
Keyword(s):  
Grenville Province ◽  
Nd Isotope ◽  
Isotope Evidence ◽  
Juvenile Crust

Nd isotope mapping of the Frontenac Terrane in the SW Grenville Province

2021 ◽  
Author(s):  
Alan Dickin ◽  
Jacob Strong
Keyword(s):  
Rift Zone ◽  
Geographical Location ◽  
Silica Content ◽  
Taupo Volcanic Zone ◽  
Grenville Province ◽  
Nd Isotope ◽  
Ottawa River ◽  
Crustal Block ◽  
Granitoid Rocks ◽  
Back Arc

Nd isotope analyses are presented for granitoid rocks from the western part of Frontenac Terrane in the Grenville Province of Ontario. TDM ages show no correlation with the silica content of the rocks, but instead correlate with geographical location, suggesting that the TDM ages are indicative of regional crustal formation age, and do not result from mixing between sources with different provenance ages. Based on these observations, we identify a new crustal age boundary that follows the Desert Lake – Canoe Lake fault and the Rideau Lake fault, and hence a new juvenile crustal block (Westport domain). This domain is identified as part of the ensimatic back-arc rift zone that formed the juvenile segment of the Central Metasedimentary Belt in Ontario. However, additional sampling along the Ottawa River suggests that the juvenile Westport domain does not extend into Quebec. Instead, a narrower ensialic rift zone is represented by the Marble domain in Quebec. Based on comparison with the Taupo volcanic zone and the northern Red Sea as modern analogues, we suggest that the transition from a wide ensimatic rift zone in Ontario to a narrow ensialic rift in Quebec was accommodated by transtensional motion along a zone of diffuse shear east of Ottawa.

Crustal formation in the Grenville Province: Nd-isotope evidence

2000 ◽  
Vol 37 (2-3) ◽  
pp. 165-181 ◽  
Author(s):  
A P Dickin
Keyword(s):  
North America ◽  
Grenville Province ◽  
Nd Isotope ◽  
Precambrian Shield ◽  
First Order ◽  
Isotope Evidence ◽  
Isotope Analyses

Ninety-eight new Nd-isotope analyses are presented for gneissic rocks from the Grenville Province. When combined with over 250 published Nd analyses and some unpublished analyses, these data can be used to establish a first-order crustal formation age map for most of the Grenville parautochthon and allochthonous polycyclic belt. In particular, the geographic extents of a juvenile Labradorian arc (Labradoria) and a juvenile 1.5 Ga arc (Quebecia) are defined, each with an area probably in excess of 100 000 km2. In addition, pre-1.75 Ga arcs are identified in Ontario (Barilia) and Labrador (Makkovikia). This work largely fills the last major gap in the continent-wide crustal formation age map of the Precambrian Shield of North America.

Sign in / Sign up

Export Citation Format

Share Document